Interaction of dihydrogen with small and light molecules.

Abstract

Using MP2, RI-MP2, MP2-R12, and CCSD(T) quantum chemical methods, the interaction energies between molecular hydrogen (H2) and the small molecules HF, H2O, NH3, and LiOH were systematically evaluated across multiple adsorption geometries. For H2O and NH3, an end-on orientation at the O or N atom proved most stable, whereas side-on configurations were preferred for HF and LiOH. Basis-set-limit CCSD(T) interaction energies were determined to be 4.40, 2.67, 3.02, and 10.74 kJ mol⁻¹ for HF, H2O, NH3, and LiOH, respectively. Simultaneous coordination of H2 to two LiOH molecules did not substantially raise the interaction energy beyond the single-molecule value. MP2-level calculations further yielded interaction energies of 2.78, 5.00, and 6.30 kJ mol⁻¹ for glycine, the glycine dimer, and imidazolium chloride, respectively.

Mechanism

H2 adopts end-on or side-on orientations depending on the electronic character of the partner molecule, with stabilization arising from dispersion and electrostatic interactions quantified at the CCSD(T) basis-set limit.